Cleanup: use C++ compatible struct declarations for Python API

Also add m_base & ob_base comments.

source/blender/python/generic/blf_py_api.c

@@ -461,7 +461,7 @@ static PyMethodDef BLF_methods[] = {
 
 PyDoc_STRVAR(BLF_doc, "This module provides access to Blender's text drawing functions.");
 static PyModuleDef BLF_module_def = {
-    PyModuleDef_HEAD_INIT,
+    /*m_base*/ PyModuleDef_HEAD_INIT,
     /*m_name*/ "blf",
     /*m_doc*/ BLF_doc,
     /*m_size*/ 0,